Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, Switzerland.Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.Department of Palaeontology and Museum, University of Zurich, Zurich, Switzerland.

UWA Oceans Institute, The University of Western Australia, Perth, WA, Australia.School of Biological Sciences, The University of Western Australia, Perth, WA, Australia.Lions Eye Institute, The University of Western Australia, Perth, WA, Australia.Oceans Graduate School, The University of Western Australia, Perth, WA, Australia.

Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, Switzerland.Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.

UWA Oceans Institute, The University of Western Australia, Perth, WA, Australia.School of Biological Sciences, The University of Western Australia, Perth, WA, Australia.Lions Eye Institute, The University of Western Australia, Perth, WA, Australia.

Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, Switzerland.Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.

Fish catch color with rods

Vertebrates are typically thought to have a consistent system for processing light, in which multiple cone opsins permit color vision during the day, but a single rod opsin provides only monochrome vision in the dark. Musilova et al. analyzed more than 100 deep-sea fish genomes and found a previously unknown proliferation of rod opsin genes that generate rod opsin photopigments that are tuned to different wavelengths of light. These receptors may allow the fish to perceive bioluminescent signals that pervade their deep-sea environment. These results reveal a previously undescribed visual system that allows for color vision in the dark.

Abstract

Vertebrate vision is accomplished through light-sensitive photopigments consisting of an opsin protein bound to a chromophore. In dim light, vertebrates generally rely on a single rod opsin [rhodopsin 1 (RH1)] for obtaining visual information. By inspecting 101 fish genomes, we found that three deep-sea teleost lineages have independently expanded their RH1 gene repertoires. Among these, the silver spinyfin (Diretmus argenteus) stands out as having the highest number of visual opsins in vertebrates (two cone opsins and 38 rod opsins). Spinyfins express up to 14 RH1s (including the most blueshifted rod photopigments known), which cover the range of the residual daylight as well as the bioluminescence spectrum present in the deep sea. Our findings present molecular and functional evidence for the recurrent evolution of multiple rod opsin–based vision in vertebrates.